We estimate the influence of the discrepancy of the cross sectional shapes between the magnetic flux tube and the equi-potential surface at the mirror throats of the anchor cell on the radial drift of the plug potential bounce ion. The radial potential profiles are assumed to be Gaussian. It is found that the discrepancy enhances the radial drift of the bounce ion and the spread radial potential profile moderates the enhancement. The radial potential profile of the core plasma is adjusted by controlling the electrostatic potentials of the coaxially separated end plate. It is found that the spread type of radial potential profile is effective for the retardation of the radial transport of the bounce ions.